1. Field of the Invention
The present invention relates to a technology for controlling reading of an untargeted page of an original in an image forming apparatus.
2. Description of the Related Art
Recently, spread of personal computers (PC) and the Internet leads to an increase in the amount and types of digital contents that are created. Due to this, a data embedding technology (a digital watermarking technology) is used as one of security control methods of digital sensitive documents that are used over a network. For example, Japanese Patent Application Laid-open No. 2000-106624 discloses a technology for embedding watermark data that cannot be perceived by humans. In the technology, image data is subjected to wavelet transformation, and redundancy of a frequency space is used to embed the watermark data into the image data.
Although realizing the digital watermarking technology in a binary image such as a document image is difficult due to less redundancy in the document image, various methods are known that use characteristics that are specific to the document image. For example, in a method disclosed in Japanese Patent No. 3136061, a base line of lines is moved to embed the watermark data into the document image. Further, in other methods disclosed in Japanese Patent Application Laid-open No. H9-186603, a blank length between words is adjusted to embed the watermark data. Further, in another method disclosed in Japanese Patent No. 3373811, the watermark data is embedded by treating the document image as a black and white binary bitmap image.
The digital content mentioned above is also printed and used as a paper document. Recently, because a high resolution output is enabled using an image forming apparatus such as a printer, various printer friendly data embedding technologies (digital watermarking technologies) have also been suggested. For example, in technologies that are disclosed in Japanese Patent Application Laid-open No. 2001-197297 and Japanese Patent Application Laid-open No. 2001-238075, when outputting content data using the printer, an image as a faint background pattern is overlapped in a background of the content data and output. In an original document (a printed material that is output by the printer), the faint background pattern appears merely as a pattern or a background color to a human eye. However, upon duplicating the original document using a copier, the faint background pattern appears on the duplicated document as predetermined characters. Therefore, actions of a person who has duplicated the original document can be checked similarly as by using a sheet for counterfeit prevention.
Further, in a method that is disclosed in Japanese Patent Application Laid-open No. H9-179494 and used as a digital watermarking method for a black and white binary document that is most widely used as the printed material, data is digitalized and expressed using a distance between a reference point mark and a position distinguishing mark (number of dots).
Thus, the data, which has been embedded using the data embedding technology mentioned earlier, is used as preventive measures for preventing fraudulent duplication or editing of the document. For example, a password can be embedded as the embedded data so that duplication or editing of the document is restricted to an authorized user.
However, in the conventional technologies mentioned above, the embedded data, which has been embedded in the image data itself, is used for protection of the original image such as prevention of unauthorized use, protection of copyrights, or prevention of falsification of data. Therefore, the conventional technologies do not cover a technology for deleting unnecessary image data and maintaining only the minimum necessary image data.
For example, when copying image data, scanning image data, or transmitting image data using a facsimile, it is desirable to omit output of unnecessary image data of unnecessary pages of an original, storage of the unnecessary image data in a memory, or transmission of the unnecessary image data. For preventing the output, storage, or transmission of the unnecessary image data, the user needs to eliminate the unnecessary pages from the original before placing the original in a placing unit, thus putting a significant burden on the user. Further, reading the image data without distinguishing between necessary pages and unnecessary pages results in storage of the unnecessary image data. As a result, a performance of the image forming apparatus such as a multifunction peripheral (MFP) is degraded.